In recent years, advances in technology, as well as ever-evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the complexity of the electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles. Such alternative fuel vehicles typically use one or more electric motors, perhaps in combination with another actuator, to drive the wheels. Additionally, such automobiles may also include other motors, as well as other high voltage components, to operate the other various systems within the automobile, such as the air conditioner.
Due to the fact that alternative fuel automobiles typically include only direct current (DC) power supplies, direct current-to-alternating current (DC/AC) inverters (or power inverters) are provided to convert the DC power to alternating current (AC) power, which is generally required by the motors. Such vehicles, particularly fuel cell vehicles, also often use two separate voltage sources, such as a battery and a fuel cell, to power the electric motors that drive the wheels. Thus, power converters, such as direct current-to-direct current (DC/DC) converters, are typically also provided to manage and transfer the power from the two voltage sources.
High-power-density inverters often employ liquid cooling where the switches, attached to a substrate and/or base plate, are mounted on a liquid cooled heat sink. A conventional three phase inverter is made from three half bridges or legs. The traction power in automotive applications is such that it is difficult to have the three half bridges assembled on a single substrate. Additionally, having all the switches on a single substrate presents challenges in attaching a large substrate to a base plate or heat sink, adversely affecting the thermal performance and reliability of the inverter. As a result, the half bridges are assembled on separate substrates, which are then packaged with or without a base plate to form a three phase (e.g., phases A, B, and C) inverter.
Typically, the capacitive coupling between phase A and phase B is not the same as the coupling between phase B and phase C or the coupling between C and A, and vice versa. The busbar length from the switches to the DC link capacitor and AC output are also not the same for all the phases, resulting in unequal stray inductances and resistances for the three phases. Unequal parasitic effects in three phases result in unequal distribution of losses on the three substrates, adversely affecting the long term reliability of the inverter. Additionally, if the power requirements are changed, more switches may need to be added to the substrates. Further, if a dual inverter is desired, considerable changes in packaging may be required, resulting in increased inverter foot print, volume, and cost.
Therefore, it is desirable to provide an inverter layout with improved performance as related to the characteristics described above, as well as a layout that allows for advanced thermal management. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent description taken in conjunction with the accompanying drawings and the foregoing technical field and background.